https://bugs.kde.org/show_bug.cgi?id=527160
Bug ID: 527160
Summary: ksystemstats_xe_helper keeps Intel xe GPU out of RC6 :
doubles idle power, breaks s2idle
Classification: Frameworks and Libraries
Product: ksystemstats
Version First 6.8.0
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: General
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
DESCRIPTION
ksystemstats_xe_helper (new in 6.8, runs with cap_perfmon) keeps the Intel GPU
from
entering idle. Power draw roughly doubled after updating to 6.8, and the laptop
stays warm while suspended.
STEPS TO REPRODUCE
1. Intel GPU on the xe driver, Plasma 6.8
2. Log in, leave the desktop idle
3. Read /sys/class/drm/card0/device/tile0/gt*/gtidle/idle_residency_ms twice, a
few seconds apart
OBSERVED RESULT
- GPU idle residency is 0% on both gt0 and gt1 (the media GT too, which nothing
is using)
- Actual GPU work per DRM fdinfo is low, so the GPU is being held awake, not
kept busy
- ksystemstats_xe_helper has cap_perfmon and seems to keep xe PMU counters open
the whole time it runs
- Pausing the helper with SIGSTOP doesn't help: it stays alive with the
counters still open, and the GPU stays at 0% idle
- Killing the helper closes the counters, and the GPU starts idling immediately
(gt0 ~50-60%, gt1 ~25-60%). So having the counters open is enough to block
idle, polling or not
- 6.8 specific: the 6.7.5 package only shipped ksystemstats_intel_helper.
ksystemstats_xe_helper is new in 6.8, and the drain started exactly at the 6.8
update
- Battery draw 7-11 W, was 4-6 W on 6.7.5 with the same apps
- s2idle drain ~7%/hour, was ~0.6%/hour
EXPECTED RESULT
Collecting GPU stats shouldn't keep the GPU awake.
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.8.0
KDE Frameworks Version: 6.31.0
Qt Version: 6.12.0
ADDITIONAL INFORMATION
Kernel 7.2.9-2-cachyos, Wayland, Mesa 26.2.4
Framework laptop, Intel Core Ultra X7 358H / Arc B390 (xe driver)
Possibly related: plasma/ksystemstats!151 notes the Xe helper never closes its
FDs (infinite loop).
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